[Fe(diene)(CO)3] complexes as a guide in stereocontrol. Applications to the asymmetric synthesis of natural products

Abstract

The ability of iron tricarbonyl units to control the region- and stereo-chemistry of nucleophilic addition to a neighbouring CX (X = O, N) double bond and 1,5-nucleophilic substitution via a η⁵-cation intermediate are described. We investigated the potential of acyclic [Fe(diene)(CO)₃] complexes as chiral auxiliaries for the asymmetric synthesis of natural products. The asymmetric syntheses of (+) and (–)-frontalin, a hydroxyethylidene dipeptide isostere, a piperidine alkaloid (SS20846A), and N-Boc-O-Me-(2R,3S,5E,7E)-2-aminotetradeca- 5,7-dien-3-ol were achieved by using the stereodirecting ability and mobility of the Fe(diene)(CO)₃ group. In addion, we developed an efficient method for synthesizing chiral dienal Fe(CO)₃ complexes, which are versatile starting materials for the asymmetric synthesis of the biologically active natural products described above.